But the region's approximately 100,000 elk are more loosely managed. Researchers say brucellosis has been spreading within elk herds and showing up in new areas in recent decades.
"Not only has the geographic range expanded, but in some areas the (rate of infections) has increased," State Veterinarian Marty Zaluski told commissioners.
Officials have shied away from the capture and slaughter of diseased elk — a controversial approach that has been used in Wyoming with some success but at great cost.
Members of the Gallatin Wildlife Association, a sporting group, had urged the commission not to adopt the plan, saying the proposal needed more public input and could prove too costly.
In the last decade alone at least 14 brucellosis infections in livestock were reported in Montana, Idaho and Wyoming. Elk were named as the likely source of the disease in most cases.
Some of the infections triggered harsh sanctions against the region's lucrative livestock industries by the U.S. Department of Agriculture. The federal government and livestock officials in other states have more recently softened their stance, largely due to more aggressive testing and vaccine programs for Yellowstone area livestock.
A brucellosis monitoring initiative for Montana elk that began two winters ago has so far found new cases of the disease in southwest Montana's Ruby Valley and the nearby Gravelly and Snowcrest ranges south of Dillon. About 12 percent of the animals captured tested positive for exposure to the disease.
More tests are planned on elk in the southern Pioneer Mountains this winter and in the Tobacco Root Mountains in the winter of 2013-2014.